The true story behind Natalie Dormer's racy Georgian in The Scandalous Lady W

I knew the basics about Lady Worsley: she had been at the centre of one of the 18th-century’s greatest sex scandals. Prior to running off with her lover, Captain Maurice George Bisset in November 1781, she had been the wife of Sir Richard Worsley, an MP and Privy Counsellor.

As the law forbade women from initiating divorce proceedings, Seymour had hoped her elopement would force Sir Richard into taking this step – however, her scheme backfired catastrophically. Instead of issuing proceedings for divorce, the outraged baronet set out to sue his friend Captain Bisset for criminal conversation, or adultery.

In 18th-century law, women were the property of their husbands, and any man who damaged the property of another man could be sued in court. The trick was first to prove that the damage or “unlawful sexual intercourse” had occurred, which necessitated the calling of witnesses, such as servants, coachmen and hotel staff to testify to what they saw. Just like us, Georgian England loved gossip, and as criminal conversation trials were heard in open court, the titillating confessions provided great entertainment.

However, the details revealed in the case of Worsley v Bisset shocked the nation. More surprising still, I was to learn that Seymour had been regarded as a scarlet woman years before the trial and even before Sir Joshua Reynolds painted her as one. As the joint heiress of her late father’s considerable fortune, Seymour Fleming’s life was never destined to be an ordinary one. While still a young lady barely out of the nursery, rumours circulated that she was worth anything from £77,000 to £100,000, an astronomical sum and the equivalent of hundreds of millions today.

It’s believed that she was the one who set her sights on the handsome baronet, Sir Richard Worsley. Sir Richard, with his title, property and political aspirations, seemed promising husband material and by September 1775, it was said they had been married “for love and £80,000”.

In spite of these auspicious beginnings, all was not well behind closed doors. The 17-year-old Lady Worsley was wholly unprepared for what awaited her in the bedchamber. Sir Richard had a vice: voyeurism. He preferred watching sex to engaging in it. Later she was to complain that “he gave me the miserable pleasure of keeping my virginity three months after marriage”.

Although her marriage roved to be a disappointment, Seymour had never been one to quietly accept her lot in life. While it was the headiness of love that inspired Seymour to run off with Bisset, it was revenge that fuelled Sir Richard's decision to sue his former friend for £20,000 in damages.

The only hope Lady Worsley had of saving Bisset from ruin was to expose all the sordid secrets of her marriage in court, thus damning herself as being a “possession” without value. The jury agreed. Though they found in favour of her husband, they awarded him just one shilling in damages.

Sir Richard and Lady Worsley remained shackled together until his death in 1805. It was only then that Seymour was able to claim back what remained of her fortune. In an unorthodox move she also reclaimed her identity by reverting to her maiden name of Fleming.

And lest anyone should forget that the scandalous Lady W did as she pleased when it came to love, at the age of 47 she married again, this time to a man 21 years her junior.

The Scandalous Lady W is on Monday 17th at 9.00pm on BBC2